Linear solenoid and manufacturing method of the same

ABSTRACT

An inner diameter of a third stator core is greater than an inner diameter of a second stator core. When a first stator core, the second stator core, and the third stator core are placed in an inner periphery of a coil, a jig is inserted from an inner-periphery opening of a first end side of the third stator core into the third stator core to directly position the first stator core, the second stator core, and the third stator core in a radial direction. Therefore, a side force generated by an axis deviation between the first stator core, the second stator core, and the third stator core can be reduced.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2013-193686filed on Sep. 19, 2013, the disclosure of which is incorporated hereinby reference.

TECHNICAL FIELD The present disclosure relates to a linear solenoidwhich outputs a force acting in an axial direction. BACKGROUND

JP-2005-045217A (US 2004/0257185 A1) discloses a linear solenoid mountedto a vehicle outputs a thrust using a magnetic flux generated accordingto an energization of a coil.

In the linear solenoid, a movement amount of a movable core in an axialdirection can be increased without increasing a size of the linearsolenoid in the axial direction. The movable core includes a cylindricalportion. Stator cores are placed at positions inside of the movable coreand outside of the movable core, respectively.

A better configuration of the linear solenoid according toJP-2005-045217A includes the movable core, a first stator core, a secondstator core, and a third stator core, which are made of magneticmaterial.

The movable core includes a magnetic portion having a cylindrical shape,and is placed in an inner periphery of the coil and is movable withrespect to an axial direction concentric with the coil. The first statorcore is placed at a position inside of an inner periphery of the movablecore, and the first stator core receives and transmits the magnetic fluxin a radial direction of the movable core. The second stator core is amagnetic portion having a cylindrical shape, and is placed at a positionoutside of an outer periphery of the movable core such that the movablecore is interposed between the first stator core and the second statorcore. The second stator core receives and transmits the magnetic flux inthe radial direction of the movable core. The third stator core isplaced at a position such that the third stator core is not in contactwith the second stator core in the axial direction. The third statorcore magnetically attracts the movable core in the axial direction.

However, the first stator core, the second stator core, and the thirdstator core can be directly positioned in the radial direction.

According to JP-2005-045217A, a magnetic portion provided integrallywith the first stator core and a magnetic portion provided integrallywith the second stator core are fitted to each other to position thefirst stator core and the second stator core in the axial direction.

Therefore, the first stator core, the second stator core, and the thirdstator core is insufficiently positioned in the radial direction, and itis possible that a side force generated by an axis deviation between thefirst stator core, the second stator core, and the third stator coreincreases. In this case, the side force is an attractive force generatedbetween the movable core, the first stator core, the second stator core,and the third stator core, in the radial direction.

SUMMARY

The present disclosure is made in view of the above matters, and it isan object of the present disclosure to provide a linear solenoid inwhich a movable core includes a cylindrical portion and stator cores areplaced at inner and outer periphery of the cylindrical portion, so as toreduce a side force.

According to an aspect of the present disclosure, a linear solenoidoutputs a thrust in an axial direction using a magnetic flux generatedaccording to an energization of a coil. The linear solenoid includes amovable core, a first stator core, a second stator core, and a thirdstator core.

The movable core includes a magnetic portion having a cylindrical shape,and is placed in an inner periphery of the coil and is movable withrespect to an axial direction concentric with the coil. The first statorcore made of magnetic material is placed at a position inside of aninner periphery of the movable core, and the first stator core receivesand transmits the magnetic flux in a radial direction of the movablecore.

The second stator core is a magnetic portion having a cylindrical shape,and is placed at a position outside of an outer periphery of the movablecore such that the movable core is interposed between the first statorcore and the second stator core. The second stator core receives andtransmits the magnetic flux in the radial direction of the movable core.The third stator core is a magnetic portion having a cylindrical shape,and is placed at a position of the first end side in the axial directionwith respect to the second stator core such that the third stator coreis not in contact with the second stator core. The third stator coremagnetically attracts the movable core toward the first end side of themovable core into the inner periphery of the third stator core, thethird stator core including an inner-periphery opening at a first endside in the axial direction where the inner-periphery opening is blockedby a cover. The third stator core has an inner diameter that is greaterthan an inner diameter of the second stator core.

When the first stator core, the second stator core, and the third statorcore are placed in the inner periphery of the coil, a jig is insertedfrom an inner-periphery opening of a first end side of the third statorcore into the third stator core to directly position the first statorcore, the second stator core, and the third stator core in a radialdirection. Therefore, a side force generated by an axis deviationbetween the first stator core, the second stator core, and the thirdstator core can be reduced. In this case, the side force is anattractive force generated between the movable core, the first statorcore, the second stator core, and the third stator core, in the radialdirection.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentdisclosure will become more apparent from the following detaileddescription made with reference to the accompanying drawings. In thedrawings:

FIG. 1 is a sectional view showing a linear solenoid;

FIG. 2A is a sectional view showing a movable part of the linearsolenoid;

FIG. 2B is a front view showing the movable part of the linear solenoid;

FIG. 3 is a sectional view showing a fixed part of the linear solenoidbefore being molded.

FIG. 4 is a sectional view showing a length in an axial direction whichrelates to a magnetic flux received and transmitted between a firststator core and a movable core;

FIG. 5A is a sectional view showing a first magnetic body;

FIG. 5B is a front view showing the first magnetic body;

FIG. 6 is a front view showing a bobbin and a terminal;

FIG. 7 is a front view showing a third magnetic body; and

FIG. 8 is a diagram showing a fluid level in the linear solenoid.

DETAILED DESCRIPTION

Embodiments of the present disclosure will be described hereafterreferring to drawings. In the embodiments, a part that corresponds to amatter described in a preceding embodiment may be assigned with the samereference numeral, and redundant explanation for the part may beomitted. When only a part of a configuration is described in anembodiment, another preceding embodiment may be applied to the otherparts of the configuration. The parts may be combined even if it is notexplicitly described that the parts can be combined. The embodiments maybe partially combined even if it is not explicitly described that theembodiments can be combined, provided there is no harm in thecombination.

Referring to drawings, a linear solenoid 1 according to an embodiment ofthe present disclosure will be described.

The linear solenoid 1 generates a magnetic attractive force as a thrustusing a magnetic flux generated according to an energization of a coil2. For example, the linear solenoid 1 may be mounted to a vehicle to beapplied to a supplier supplying an oil pressure of a valve-timingmechanism that changes a valve timing of an internal combustion engine.

The linear solenoid 1 includes a movable core 3, a first stator core 4,a second stator core 5, and a third stator core 6. The first stator core4, the second stator core 5, and the third stator core 6 correspond tomagnetic portions.

The movable core 3 is a magnetic body having a cylindrical shape, and isplaced in an inner periphery of the coil 2 and is movable with respectto an axial direction concentric with the coil 2. Alternatively, themovable core 3 may be a member including the magnetic body. The movablecore 3 includes a first introducing passage 8 through which a fluid isintroduced between a first end side of the movable core 3 and a secondend side of the movable core 3 in the axial direction. As shown in FIGS.2A and 2B, two first introducing passages 8 are provided in an innerperipheral surface of the movable core 3 at a 180-degrees interval. Thefirst introducing passages 8 are both provided to penetrate the movablecore 3 in the axial direction and correspond to grooves opened to theinner peripheral surface of the movable core 3.

The first stator core 4 having a cylindrical shape is a part of a firstmagnetic body 9. The first magnetic body 9 corresponds to a fixedmember. The first stator core 4 is placed at a position inside of aninner periphery of the movable core 3, and slidably supports the movablecore 3 in the axial direction. The first stator core 4 receives andtransmits the magnetic flux in a radial direction of the movable core 3.

The second stator core 5 is having a cylindrical shape is a part of asecond magnetic body 10 that is different from the first magnetic body9. The second stator core 5 is placed at a position outside of an outerperiphery of the movable core 3 such that the movable core 3 isinterposed between the first stator core 4 and the second stator core 5.The second stator core 5 receives and transmits the magnetic flux in theradial direction of the movable core 3. In addition, a gap is generatedbetween an inner peripheral surface of the second stator core 5 and anouter peripheral surface of the movable core 3. The movable core 3slides in the axial direction without being in contact with the secondstator core 5.

The third stator core 6 having a cylindrical shape is a part of a thirdmagnetic body 11 that is different from the first magnetic body 9 andthe second magnetic body 10. The third stator core 6 is concentric withthe second stator core 5 and is placed at a position of the first endside in the axial direction with respect to the second stator core 5such that the third stator core 6 is not in contact with the secondstator core 5. The third stator core 6 magnetically attracts the movablecore 3 toward the first end side of the movable core 3 into an innerperiphery of the third stator core 6.

A cover 12 is provided to block an inner-periphery opening of a firstend side of the third stator core 6 in the axial direction. The cover 12is different from the first magnetic body 9, the second magnetic body10, and the third magnetic body 11. The first end side of the thirdstator core 6 is opposite to a second end side of the third stator core6 where the second stator core 5 is placed. The cover 12 prevents aforeign matter from entering the linear solenoid 1 from external. Thecover 12 includes a cover portion 13 having an angled shape such as anumbrella, and the cover portion 13 is placed at a first end side of thecover 12 in the axial direction to prevent the foreign matter fromentering the linear solenoid 1 from external. The cover 12 furtherincludes a first cylindrical portion 14 which is pressed into the innerperiphery of the third stator core 6. An area for receiving andtransmitting the magnetic flux increases according to the firstcylindrical portion 14.

As shown in FIG. 3, in the linear solenoid 1, an inner diameter a of thethird stator core 6 is greater than an inner diameter b of the secondstator core 5. The inner diameter a and the inner diameter b are greaterthan an outer diameter c of the first stator core 4. When the firststator core 4, the second stator core 5, and the third stator core 6 areplaced in the inner periphery of the coil 2, a jig 15 is inserted fromthe inner-periphery opening of the first end side of the third statorcore 6 into the third stator core 6 to directly position the firststator core 4, the second stator core 5, and the third stator core 6 inthe radial direction.

The linear solenoid 1 further includes a first receiving andtransmitting mechanism (first R/T mechanism) a and a second R/Tmechanism β.

The first R/T mechanism a makes a magnetic portion of the secondmagnetic body 10 different from the second stator core 5 be in contactwith a magnetic portion of the third magnetic body 11 different from thethird stator core 6, so as to receives and transmits the magnetic fluxbetween the magnetic portion of the second magnetic body 10 and themagnetic portion of the third magnetic body 11.

The second magnetic body 10 includes a second end yoke 16 having aring-plate shape. The second end yoke 16 outwardly extends from a secondend side of the second stator core 5 and covers a second end side of thecoil 2, in the axial direction. The third magnetic body 11 includes afirst end yoke 17 having a ring-plate shape, and an outer yoke 18. Thefirst end yoke 17 outwardly extends from the first end side of the thirdstator core 6 and covers a first end side of the coil 2, in the axialdirection. The outer yoke 18 having a cylindrical shape extends from anouter periphery of the first end yoke 17 toward a second end side of theaxial direction and covers the coil 2. The third magnetic body 11further includes a first flange portion 19. The first flange portion 19having a ring-plate shape outwardly extends from a second end side ofthe outer yoke 18 in the axial direction.

The second end yoke 16 includes a first outer-periphery portion 20 whichis in surface contact with the first flange portion 19 according to thefirst R/T mechanism α. Therefore, the magnetic flux is received andtransmitted between the first outer-periphery portion 20 and the firstflange portion 19.

The second end yoke 16 extends to a position outside of an outerperiphery of the coil 2, and the first outer-periphery portion 20 isplaced at a position outside of the outer periphery of the coil 2. Thefirst outer-periphery portion 20 includes a first outer-peripherysurface 20 a at a first end side of the first outer-periphery portion20. The first outer-periphery surface 20 a is a surface perpendicular tothe axial direction. The first flange portion 19 includes a flangesurface 19 b at a second end side of the first flange portion 19. Theflange surface 19 b is a surface perpendicular to the axial direction.

Since the first outer-periphery surface 20 a and the flange surface 19 bare in surface contact with each other, the magnetic flux is receivedand transmitted between the second magnetic body 10 and the thirdmagnetic body 11, outside of the coil 2.

In addition, since the first flange portion 19 and the firstouter-periphery portion 20 are not fitted to each other by a male-femalefitting, the first flange portion 19 and the first outer-peripheryportion 20 can relatively move with respect to each other in the radialdirection in a case where the jig 15 positions the second magnetic body10 and the third magnetic body 11.

The second R/T mechanism β makes a magnetic portion of the firstmagnetic body 9 different from the first stator core 4 be in contactwith a magnetic portion of the second magnetic body 10 different fromthe second stator core 5, so as to receives and transmits the magneticflux between the magnetic portion of the first magnetic body 9 and themagnetic portion of the second magnetic body 10.

The first magnetic body 9 includes a second flange portion 21. Thesecond flange portion 21 having a ring-plate shape outwardly extendsfrom a second end side of the first stator core 4 in the axialdirection.

The second end yoke 16 further includes a first inner-periphery portion23 which is in surface contact with a second outer-periphery portion 24of the second flange portion 21 according to the second R/T mechanism β.Therefore, the magnetic flux is received and transmitted between thefirst inner-periphery portion 23 and the second outer-periphery portion24.

The second flange portion 21 extends to a position outside of the outerperiphery of the movable core 3, and the second outer-periphery portion24 is placed at a position outside of the outer periphery of the movablecore 3. The first inner-periphery portion 23 includes an inner-peripherysurface 23 b at a second end side of the first inner-periphery portion23. The inner-periphery surface 23 b is a surface perpendicular to theaxial direction. The second outer-periphery portion 24 includes a secondouter-periphery surface 24 a at a first end side of the secondouter-periphery portion 24. The second outer-periphery surface 24 a is asurface perpendicular to the axial direction.

Since the second outer-periphery surface 24 a and the inner-peripherysurface 23 b are in surface contact with each other, the magnetic fluxis received and transmitted between the first magnetic body 9 and thesecond magnetic body 10, at a position adjacent to the second end sideof the coil 2.

In addition, since the first inner-periphery portion 23 and the secondouter-periphery portion 24 are not fitted to each other by a male-femalefitting, the first inner-periphery portion 23 and the secondouter-periphery portion 24 can relatively move with respect to eachother in the radial direction in a case where the jig 15 positions thefirst magnetic body 9 and the second magnetic body 10.

The first R/T mechanism α is placed at a first end side of the axialdirection of the second R/T mechanism β.

The linear solenoid 1 further includes a notch portion 25 whichpenetrates the second end yoke 16 in the axial direction. The coil 2includes a terminal 26 extends from the notch portion 25. The first R/Tmechanism α is placed at the first end side of the terminal 26.

The linear solenoid 1 further includes a bearing 28, an output member29, and a bobbin 30.

The bearing 28 is fixed to the inner periphery of the movable core 3 anddirectly slides with respect to the first stator core 4. The movablecore 3 indirectly slides with respect to the first stator core 4 via thebearing 28. The bearing 28 includes an outer-periphery part that is madeof magnetic material, and an inner-periphery part that is made ofnon-magnetic material. The bearing 28 further includes an innerperiphery surface that is made of non-magnetic material and is directlyin contact with an outer periphery surface of the first stator core 4.

A first area is an area in the inner periphery surface of the movablecore 3 where the magnetic flux can be received and transmitted betweenthe inner periphery surface of the movable core 3 and the outerperiphery surface of the first stator core 4 in the radial direction. Alength of the first area in the axial direction is referred to as afirst length d. A second area is an area in the outer periphery surfaceof the first stator core 4 where the magnetic flux can be received andtransmitted between the outer periphery surface of the first stator core4 and the inner periphery surface of the movable core 3 in the radialdirection. A length of the second area in the axial direction isreferred to as a second length e. As shown in FIG. 4, the first length dis less than the second length e. Further, the first length d issubstantially equal to a length of the bearing in the axial direction.

The bearing 28 includes a third flange portion 32 which outwardlyextends from a second end side of the bearing 28 in the axial direction.The third flange portion 32 limits a movement of the movable core 3toward the second end side of the axial direction by being in contactwith a second inner-periphery portion 33 of the second flange portion21. The third flange portion 32 includes a first end part that is placedat a first end side of the third flange portion 32 and is made ofmagnetic material, and a second end part that is placed at a second endside of the third flange portion 32 and is made of non-magneticmaterial. The third flange portion 32 further includes an abuttingsurface 32 b that is made of non-magnetic material and is directly incontact with the second inner-periphery portion 33.

As shown in FIG. 5, second introducing passages 34 are provided in asurface of a first end side of the second inner-periphery portion 33 inthe axial direction as grooves through which the fluid is introducedbetween an inner periphery of the third flange portion 32 and an outerperiphery of the third flange portion 32. According to the presentembodiment, the second introducing passages 34 are provided around anaxial center of the linear solenoid 1 at a 60-degrees interval. Further,the second introducing passages 34 are radially placed.

The output member 29 that is made of non-magnetic material is fixed tothe movable core 3, and moves together with the movable core 3 toward afirst end side of the axial direction to outputs the thrust. When theoutput member 29 receives a recovery force from an external device, theoutput member 29 is moved together with the movable core 3 toward thesecond end side of the axial direction.

The output member 29 includes a fixed portion 36 and a shaft portion 37.The fixed portion 36 is a cylindrical shape and is fixed to the movablecore 3 to be concentric with the movable core 3. The shaft portion 37 isa column shape and extends toward the first end side of the axialdirection.

The inner periphery of the movable core 3 includes a step surface at thefirst end side of the movable core 3 in the axial direction. A diameterof the step surface is greater than a diameter of a common part of theinner periphery. In this case, the common part of the inner periphery isa part of the inner periphery other than the step surface. The fixedportion 36 is inserted into an area including the step surface and isfixed to the movable core 3. The bearing 28 is inserted into an areaincluding the common part and is fixed to the movable core 3. As shownin FIG. 2A, a gap f is generated between the bearing 28 and the fixedportion 36. The gap f communicates with the first introducing passage 8.

An opening 38 is formed by the cover portion 13 such that the shaftportion 37 penetrating the opening 38 in the axial direction. Therefore,the shaft portion 37 outputs the thrust to external devices.

The shaft portion 37 has a diameter less than a diameter of the fixedportion 36. The shaft portion 37 and the fixed portion 36 are seamlesslybonded to each other via a taper portion 39. The taper portion 39expanses its diameter toward the second end side of the axial direction.A first end side of the first stator core 4 relatively moves withrespect to an inner periphery of the fixed portion 36. The first endside of the first stator core 4 is chamfered to have a taper shape. Eventhough the movable core 3 and the output member 29 moves to positionsmost close to the second end side of the first stator core 4, an innerperiphery of the taper portion 39 are not in contact with the firststator core 4.

The bobbin 30 is a member made of resin and is wound by the coil 2. Thebobbin 30 includes a second cylindrical portion 40, a fourth flangeportion 41 a, and a fifth flange portion 41 b.

The second cylindrical portion 40 is placed at a position outside ofboth the second stator core 5 and the third stator core 6. The secondcylindrical portion 40 is wound by the coil 2. The fourth flange portion41 a and the fifth flange portion 41 b outwardly extend from a first endside of the second cylindrical portion 40 and a second of the secondcylindrical portion 40, respectively, so as to define a coil area wherethe coil 2 is wound. The linear solenoid 1 includes a first end seal γand a second end seal δ which protect the coil 2 from the fluid enteringthe linear solenoid 1.

The first end seal γ is provided to surround an axial center of the coil2 at a first end side of the fourth flange portion 41 a in the axialdirection. As shown in FIG. 6, a first protrusion 42 a that is made ofresin and has a ring shape surrounds the axial center of the coil 2 at asurface of the first end side of the fourth flange portion 41 a. Thefirst end seal γ is provided by being solidified after being meltedaccording to a melting resin at the first protrusion 42 a.

The second end seal δ is provided to surround the axial center of thecoil 2 at a second end side of the fifth flange portion 41 b in theaxial direction. A second protrusion 42 b that is made of resin and hasa ring shape surrounds the axial center of the coil 2 at a surface ofthe second end side of the fifth flange portion 41 b. The second endseal δ is provided by being solidified after being melted according to amelting resin at the second protrusion 42 b.

A manufacturing method of the linear solenoid 1 includes an injectionmolding step which injects a melting resin and molds the coil 2, thefirst magnetic body 9, the second magnetic body 10, the third magneticbody 11, the bobbin 30, and an attachment bracket 43. Further, the firstend seal γ, the second end seal δ, a connector 44, and a groovereceiving an O-ring 45 are formed by the melting resin injected in theinjection molding step.

As shown in FIG. 3, an injection opening (not shown) of the meltingresin in the injection molding step is placed at a position in an area gthat is opposite to a second end side of the first magnetic body 9.

The second end yoke 16 has a shape that does not interfere with thesecond protrusion 42 b. For example, the second end yoke 16 is not incontact with the second protrusion 42 b. The second end yoke 16 furtherincludes an intermediate portion 46 placed between the firstinner-periphery portion 23 and the first outer-periphery portion 20. Theintermediate portion 46 extends toward the second end side of the axialdirection. As shown in FIG. 3, the intermediate portion 46 and the fifthflange portion 41 b form a space 47 into which the second protrusion 42b protrudes. The melting resin is filled in the space 47.

The linear solenoid 1 further includes a penetrating hole 49 thatpenetrates the third stator core 6. The penetrating hole 49 communicatesan interior of the linear solenoid 1 with an exterior of the linearsolenoid 1. The penetrating hole 49 is opened at a position of thelinear solenoid 1 outward of an inner-peripheral wall 6 a of the thirdstator core 6. According to the present embodiment, the penetrating hole49 is parallel to the axial center of the linear solenoid 1. Further, aplurality of the penetrating holes 49 is provided around the axialcenter of the coil 2. As shown in FIG. 7, for example, the penetratingholes 49 may be provided around the axial center of the coil 2 at a45-degrees interval.

The linear solenoid 1 is mounted to the vehicle such that the axialdirection is substantially parallel to a horizontal direction. In thiscase, the connector 44 extends upward in a vertical direction withrespect to gravity, and the attachment bracket 43 extends downward inthe vertical direction with respect to gravity. Thus, as shown in FIG.8, a fluid level in the linear solenoid 1 is controlled to be lower thanthe inner-peripheral wall 6 a of the third stator core 6.

In the linear solenoid 1, when the coil 2 is energized, the magneticflux is received and transmitted in the radial direction between thefirst stator core 4, the second stator core 5, and the movable core 3.Further, the magnetic flus is received and transmitted in the radialdirection between the movable core 3 and the third stator core 6, andthe movable core 3 is attracted and moved toward the first end side ofthe axial direction. Thus, the linear solenoid 1 outputs the thrust inthe axial direction.

According to the present embodiment, the linear solenoid 1 includes themovable core 3 having a cylindrical shape, and the first stator core 4and the second stator core 5 which are placed at positions inward of themovable core 3 and outward of the movable core 3, respectively. Themagnetic flux is received and transmitted in the radial direction fromboth the first stator core 4 and the second stator core 5. The thirdstator core 6 is a magnetic portion and is placed at a position of thefirst end side in the axial direction with respect to the second statorcore 5 such that the third stator core 6 is not in contact with thesecond stator core 5. The third stator core 6 magnetically attracts themovable core 3 toward the first end side of the movable core 3 into theinner periphery of the third stator core 6. The cover 12 is provided toblock the inner-periphery opening of the first end side of the thirdstator core 6 in the axial direction. In the linear solenoid 1, theinner diameter a of the third stator core 6 is greater than the innerdiameter b of the second stator core 5.

When the first stator core 4, the second stator core 5, and the thirdstator core 6 are placed in the inner periphery of the coil 2, the jig15 is inserted from the inner-periphery opening of the first end side ofthe third stator core 6 into the third stator core 6 to directlyposition the first stator core 4, the second stator core 5, and thethird stator core 6 in the radial direction. Therefore, a side forcegenerated by an axis deviation between the first stator core 4, thesecond stator core 5, and the third stator core 6 can be reduced. Inthis case, the side force is an attractive force generated between themovable core, the first stator core, the second stator core, and thethird stator core, in the radial direction.

The first R/T mechanism α is provided to receive and transmit themagnetic flux by making the second end yoke 16 of the second magneticbody 10 be in contact with the first flange portion 19 of the thirdmagnetic body 11. Specifically, the first R/T mechanism α receives andtransmits the magnetic flux by making the first outer-periphery surface20 a be in surface contact with the flange surface 19 b.

Therefore, since an area for receiving and transmitting the magneticflux between the second magnetic body 10 and the third magnetic body 11can be sufficiently ensured, the magnetic attractive force can beensured by reducing a magnetic resistance.

The second R/T mechanism β is provided to receive and transmit themagnetic flux by making the second flange portion 21 of the firstmagnetic body 9 be in contact with the second end yoke 16 of the secondmagnetic body 10. Specifically, the second R/T mechanism β receives andtransmits the magnetic flux by making the second outer-periphery surface24 a be in surface contact with the inner-periphery surface 2 b.

Therefore, since an area for receiving and transmitting the magneticflux between the first magnetic body 9 and the second magnetic body 10can be sufficiently ensured, the magnetic attractive force can beensured by reducing a magnetic resistance.

The first R/T mechanism α is placed at the first end side of the axialdirection of the second R/T mechanism β.

Therefore, a size of the linear solenoid 1 can be reduced in the axialdirection. The second R/T mechanism β is necessary to be placed at aposition adjacent to the second end side of the coil 2. The first R/Tmechanism α can be placed at one of a position outward of the coil 2 anda position inward of the coil 2. Since the first R/T mechanism α isplaced at the first end side of the axial direction of the second R/Tmechanism β, the size of the linear solenoid 1 can be reduced in theaxial direction.

The injection opening of the melting resin in the injection molding stepof the linear solenoid 1 is placed at a position in an area g that isopposite to the second end side of the first magnetic body 9. Further,the injection opening is placed at a position adjacent to a second endside of the second R/T mechanism β in the axial direction.

Thus, the first outer-periphery surface 20 a can be surely in surfacecontact with the flange surface 19 b according to an injection pressureof the melting resin such that the first outer-periphery surface 20 a isfixed to the flange surface 19 b, and the second outer-periphery surface24 a can be surely in surface contact with the inner-periphery surface23 b according to an injection pressure of the melting resin such thatthe second outer-periphery surface 24 a is fixed to the inner-peripherysurface 23 b. It is unnecessary to provide specified positions for theabove surfaces to meet each other according to the first R/T mechanism αand the second R/T mechanism β.

A configuration of the linear solenoid 1 is not limited to the presentembodiment, various modifications can be applied.

According to the present embodiment, the first stator core 4 slidablysupports the movable core 3 from the inner periphery of the movable core3. However, the second stator core 5 may slidably support the movablecore 3 from the outer periphery of the movable core 3. Alternatively,the second stator core 5 may slidably support the output member 29.

According to the present embodiment, the second introducing passages 34are provided in the second flange portion 21 of the first magnetic body9. However, the second introducing passages 34 may be provided in thethird flange portion 32 of the bearing 28. Alternatively, the secondintroducing passages 34 may be provided in both the second flangeportion 21 and the third flange portion 32.

While the present disclosure has been described with reference to theembodiments thereof, it is to be understood that the disclosure is notlimited to the embodiments and constructions. The present disclosure isintended to cover various modification and equivalent arrangements. Inaddition, while the various combinations and configurations, which arepreferred, other combinations and configurations, including more, lessor only a single element, are also within the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A linear solenoid outputting a thrust in an axialdirection using a magnetic flux generated according to an energizationof a coil, the linear solenoid comprising: a movable core including amagnetic portion having a cylindrical shape, the movable core placed inan inner periphery of the coil and being movable with respect to anaxial direction concentric with the coil; a first stator core being madeof magnetic material, the first stator core placed at a position insideof an inner periphery of the movable core, the first stator corereceiving and transmitting the magnetic flux in a radial direction ofthe movable core; a second stator core corresponding to a magneticportion having a cylindrical shape, the second stator core placed at aposition outside of an outer periphery of the movable core such that themovable core is interposed between the first stator core and the secondstator core, the second stator core receiving and transmitting themagnetic flux in the radial direction of the movable core; and a thirdstator core corresponding to a magnetic portion having a cylindricalshape, the third stator core placed at a position of the first end sidein the axial direction with respect to the second stator core such thatthe third stator core is not in contact with the second stator core, thethird stator core magnetically attracting the movable core toward thefirst end side of the movable core into the inner periphery of the thirdstator core, the third stator core including an inner-periphery openingat a first end side in the axial direction where the inner-peripheryopening is blocked by a cover, wherein the third stator core has aninner diameter that is greater than an inner diameter of the secondstator core.
 2. The linear solenoid according to claim 1, furthercomprising: a first receiving and transmitting mechanism making a firstmagnetic portion provided integrally with the second stator core be incontact with a second magnetic portion provided integrally with thethird stator core, the first receiving and transmitting mechanismreceiving and transmitting the magnetic flux between the first magneticportion and the second magnetic portion, wherein the first magneticportion includes a first surface perpendicular to the axial direction,the second magnetic portion includes a second surface perpendicular tothe axial direction, and the first receiving and transmitting mechanismreceives and transmits the magnetic flux by making the first surface bein surface contact with the second surface.
 3. The linear solenoidaccording to claim 1, further comprising: a second receiving andtransmitting mechanism making a third magnetic portion providedintegrally with the first stator core be in contact with the fourthmagnetic portion provided integrally with the second stator core, thesecond receiving and transmitting mechanism receiving and transmittingthe magnetic flux between the third magnetic portion and the fourthmagnetic portion, wherein the third magnetic portion includes a thirdsurface perpendicular to the axial direction, the fourth magneticportion includes a fourth surface perpendicular to the axial direction,and the second receiving and transmitting mechanism receives andtransmits the magnetic flux by making the third surface be in surfacecontact with the fourth surface.
 4. The linear solenoid according toclaim 1, further comprising: a first receiving and transmittingmechanism making a first magnetic portion provided integrally with thesecond stator core be in contact with a second magnetic portion providedintegrally with the third stator core, the first receiving andtransmitting mechanism receiving and transmitting the magnetic fluxbetween the first magnetic portion and the second magnetic portion; anda second receiving and transmitting mechanism making a third magneticportion provided integrally with the first stator core be in contactwith the fourth magnetic portion provided integrally with the secondstator core, the second receiving and transmitting mechanism receivingand transmitting the magnetic flux between the third magnetic portionand the fourth magnetic portion, wherein the first magnetic portionincludes a first surface perpendicular to the axial direction, thesecond magnetic portion includes a second surface perpendicular to theaxial direction, the first receiving and transmitting mechanism receivesand transmits the magnetic flux by making the first surface be insurface contact with the second surface, the third magnetic portionincludes a third surface perpendicular to the axial direction, thefourth magnetic portion includes a fourth surface perpendicular to theaxial direction, the second receiving and transmitting mechanismreceives and transmits the magnetic flux by making the third surface bein surface contact with the fourth surface, and the first receiving andtransmitting mechanism is placed at a first end side of the axialdirection of the second receiving and transmitting mechanism.
 5. Thelinear solenoid according to claim 1, further comprising: a jig insertedfrom the inner-periphery opening into the third stator core to directlyposition the first stator core, the second stator core, and the thirdstator core in the radial direction.
 6. A manufacturing method of thelinear solenoid according to claim 4, comprising: injection molding thecoil, a first magnetic body including the first stator core, a secondmagnetic body including the second stator core, and a third magneticbody including the third stator core, wherein the injection moldingincludes injecting a melting resin, and molding the coil, the firstmagnetic body, the second magnetic body, and the third magnetic body,and in the injection molding step, an injection opening of the meltingresin is placed at a position in an area that is opposite to a secondend side of the first magnetic body and is placed at a position adjacentto a second end side of the second receiving and transmitting mechanismin the axial direction.